CN1201664C - Steam heater - Google Patents

Abstract

The present invention relates to an apparatus for treating a fluid product (4) such as a dairy product using heat (6), wherein the product (8) is conveyed along with steam through a product pipe to treat the product using heat from the steam, and then the heat-treated product is conveyed to an expansion container (10) to cool the product.

Description

steam heater

technical field

The present invention relates to an apparatus for utilizing heat to treat a fluid product such as a dairy product, the apparatus being provided with at least one product duct for conveying the product and steam in use for treating the product with heat from the steam; and for cooling Expansion vessel for product from a product pipeline provided with an outflow terminating in the expansion vessel, at least one steam inflow inlet, at least one product inflow inlet and a flow downstream of the steam inflow inlet and the product inflow inlet to form a flow resistance a restriction which also forms the outflow of the product conduit, such that there is no sidewall of any product conduit downstream of the restriction and which terminates directly in the expansion vessel, the product conduit being at one end of the vessel extended through the opening.

The invention also relates to a method of treating a fluid product with heat, wherein the product is conveyed through at least one product conduit with steam to treat the product with heat from the steam, and the steam-treated The product of the expansion vessel is fed to the expansion vessel to cool the product and contains in the product line a restriction under the action of which, downstream of said restriction in the expansion vessel, is formed by the product in the expansion vessel liquid droplets, the method being carried out by means of an apparatus for treating a fluid product using heat, the apparatus being provided with at least one product conduit in use for conveying the product and steam to treat the product using heat from the steam; and Expansion vessel for cooling product from a product line provided with an outflow terminating in the expansion vessel, at least one steam inflow, at least one product inflow and downstream of the steam inflow and product inflow to form a flow A flow restriction of resistance, which also forms the outflow of the product pipe, so that there is no side wall of any product pipe downstream of the restriction, and which terminates directly in the expansion vessel, the product pipe at Extending through an opening of the container.

Background technique

Such a device and method for thermally treating a fluid product in liquid form is known from US 2,022,419. The essence of this heat treatment is that the product is heated to a high temperature for a short period of time and then cooled rapidly. This heat treatment is superior to heat treatment where the product is heated to a slightly higher temperature for a longer period of time. An advantage described in this respect is that the destruction of bacteria takes place more effectively at higher temperatures. Therefore, adverse effects on products during heat treatment can be reduced, and at the same time, harmful microorganisms can be sufficiently eliminated. A disadvantage of this known device is that caking may occur on the product channel in the expansion vessel and that the temperature of the product in this part of the product channel may gradually decrease.

Contents of the invention

The present invention aims at overcoming the aforementioned disadvantages and is characterized in that the product line is connected to the container in the opening by means of a thermally insulating seal and the outflow opening is located on the surface of the inner wall of the expansion container. Since the outflow is located on the surface of the inner wall of the expansion vessel, the product leaving the restriction will be cooled directly in the expansion vessel. The fact that the outflow port is on the surface of the inner wall of the expansion vessel means that the cooled product downstream of the restriction does not cake or clog in the product duct.

By means of this device the product in the product line is heated rapidly and at the end of the product line immediately before it terminates in the expansion vessel, since the product is only kept at this temperature for a relatively short time, it is possible achieve relatively high temperatures. After flowing through the restriction, the product will be cooled directly in the expansion vessel. Due to the fact that the product is kept at the maximum temperature for a very short time, it is possible to choose this temperature higher than known devices without suffering adverse effects such as protein denaturation. On the other hand, as a consequence of the brief high temperature, the inactivation of the microorganisms will be much higher than, for example, a reduction rate of 10%.

Furthermore, in this way, the product line in the vicinity of the combined restriction and outflow opening can still retain adequate heat, while the wall of the expansion vessel is hardly heated. Thus, caking of the product on the inner wall of the expansion vessel can be prevented.

Preferably, the at least one steam supply is located downstream of the at least one product supply.

Furthermore, in particular, the volume of the product line between the at least one steam supply opening and the restriction is designed to be adjustable. This allows the product to remain hot for a variable length of time before flowing through the restriction to cool. In particular, the length of the pipe between the steam supply port and the restriction is designed to be adjustable.

Preferably, the device is dimensioned such that, in use, the steam condenses completely downstream of the restriction. In this way, the temperature before the restriction will be constant and will reach the maximum level.

In particular, the device is also provided with steam supply means for supplying pressurized steam to at least one steam supply port. Additionally, the device may be provided with sensors for sensing the temperature in a portion of the product conduit downstream of the at least one steam supply port and the at least one product supply port. In particular, the steam supply means is arranged to adjust the amount of steam supplied to the product line in accordance with the sensed temperature.

Additionally, it is preferred that the length of the restriction is approximately equal to the diameter of the restriction.

When the diameter of the restriction is 0.5-5 mm and preferably about 2 mm, obviously no steam will flow out in the restriction and thus no air bubbles will form. Thus, it is possible to prevent the flow rate from being limited due to the fact that a critical top speed has been reached. On the contrary, in the known device, the flow rate is limited by the conditions in which the steam exits in the restriction, indicated as critical in WO 84/02062.

Furthermore, especially when used in liquid products, droplets of the product are formed in the expansion vessel by means of the restriction. Thus, in the expansion vessel, an enlargement of the surface of the product occurs so that the product can be cooled rapidly.

A preferred embodiment of the invention is also characterized in that the product conduit has a diameter of approximately 12 mm, the part provided with holes extends over a length of approximately 100 mm and has a minimum of 2 (for example 30) holes provided therein, each The diameter of the holes is approximately 1 mm. In particular, the device is characterized in that the expansion vessel has a diameter of approximately 500 mm and a height of at least 500 mm.

In the known arrangement of WO 84/02062, the product line continues downstream of the restriction into the expansion vessel. Thus, the temperature of the fluid product downstream of the restriction will decrease gradually rather than suddenly. Downstream of the restriction, the fluid product is still warm due to the product piping. Consequently, the product remains warm for a relatively long time, so that the above-mentioned detrimental effects on the product are not optimally reduced during heat treatment.

In addition, the known device has the disadvantage that the product line downstream of the restriction will become dirty, since the product cakes there while the product line is still hot. This leads to the fact that the device can only be used for a relatively short time (a few hours at a rough estimate) after having to be cleaned, especially when consumables are involved.

A method capable of providing such heat treatment is disclosed in WO 98/07328. The method is a direct heat treatment method, which means that the product to be heated is brought into direct contact with steam, after which the steam condenses in the product. In the process, the product is mixed with steam in a mixing chamber, thus forming a mixture of product, steam and condensate. Here, excess steam is provided. Subsequently, this mixture is sent through a product line. Here, the residence time of the product in the product line is determined by the amount of steam supplied. The product flows through a product line, a controllable valve forming a flow restriction, and a subsequent line to the expansion vessel. The product remains at the maximum temperature T ⁽¹⁾ _max for a relatively long time. The product that has reached the expansion vessel is expanded and thereby cooled. Treated product is available through a drain in the expansion vessel. The steam leaves the expansion vessel through a separate discharge port.

In the method disclosed in WO 98/07238 the product has been heated to a higher temperature in the mixing chamber. Subsequently, this mixture is sent through a product line. This means that the product is actually at the highest heating temperature during a part of the stay in the mixing chamber, and throughout the time it is transported through the product line to the expansion vessel. This leads to a first disadvantage of the method, which is that due to this relatively long period of time, there is a limit to the maximum temperature to which the product can be heated without being adversely affected, such as protein denaturation. A second disadvantage of the above method is that the residence time in the mixing chamber is not equal for all product fractions, which is detrimental for the final quality of the product.

The method according to the invention is characterized in that the product line is connected to the container in the opening by means of a thermally insulating seal, and the outflow opening is located on the surface of the inner wall of the expansion container. Thus, in the expansion vessel, an enlargement of the surface of the product occurs, allowing rapid cooling of the product.

Description of drawings

The present invention will be further described on the basis of accompanying drawings below. In these drawings:

Figure 1 shows a schematic diagram of a known device using heat to treat products;

Figure 2 shows a possible temperature profile of a product heat-treated in the apparatus of Figure 1;

Figure 3a shows a schematic view of a first embodiment of a device for treating products with heat according to the invention;

Figure 3b shows a schematic view of a second embodiment of a device for treating products with heat according to the invention;

Figure 4 shows a possible temperature profile for the product heat-treated in Figures 3a and 3b.

Detailed ways

In FIG. 1 is shown a known device 1 for treating fluid products, such as dairy products, using heat. The product 4 is conveyed through a product conduit 8 with steam 6 for treating the product with heat from the steam. The heat-treated product is then conveyed to an expansion vessel 10 to cool the product. The device is also provided with a mixing chamber 12 in which the steam 6 is mixed with the product. In the product line there is also a valve 14 with which the pressure downstream of the valve 14 in the product line can be maintained at a certain level. The product line 8 continues downstream of the valve 14 to an outflow opening 16 in the expansion vessel 10 . The expansion vessel 10 is also provided with a product discharge 18 for discharging cooled product from the expansion vessel 10 and a steam discharge 20 for discharging steam from the expansion vessel 10 .

Fig. 3a shows a first embodiment of the device according to the invention, in Figs. 1 and 3a corresponding parts are denoted by the same reference numerals. The side wall 22 of the product duct 8 is provided with a plurality of steam supply openings 24 . Product 4 is supplied to product line 8 at a pressure of eg 4-15 bar. A steam chamber 26 is provided around a part of the product pipe 8 in which a steam supply port 24 is provided, so that with the assistance of a steam supply device 28, steam is supplied to the steam chamber at a certain pressure and then passed through the steam supply port 24 Spray into product line 8.

The flow time T ⁽¹⁾ _B of the product in the product line 8 can be achieved by means of the arrangement according to the invention in FIG. 3 a of less than 1000 ms, in particular less than 100 ms. During this time, the product is heated from a temperature T _in of 1-110°C to a temperature T _max of 80-200°C. A relevant, possible temperature profile is given in FIG. 4 . A linear time scale is included along the horizontal axis and a linear temperature scale is included along the vertical axis. In FIG. 4, T ⁽³⁾ _B is the average time the product is in the product line, and T ⁽³⁾ _D is the average time the product is cooled in the expansion vessel 10.

FIG. 2 gives a possible temperature profile for heating a product according to the prior art device of FIG. 1 . The axes of FIG. 2 have the same scale as the corresponding axes in FIG. 4 . In Fig. 2, t ⁽¹⁾ _A is the average time the product is in the mixing chamber 12, while t ⁽¹⁾ _B is the average time the product is in the product line downstream of the mixing chamber 12, and t ⁽¹⁾ _C is the average time the product is in the mixing chamber 12. The average time in the product line downstream of the valve 14 and upstream of the outlet, t ⁽¹⁾ _D is the average time for the product to cool in the expansion vessel 10. A comparison of Figures 2 and 4 shows that the product processed by the device of Figure 3a can reach a higher temperature in a shorter time than the product processed by the device of Figure 1 (t ⁽³⁾ _B <[ t ⁽¹⁾ _A +t ⁽¹⁾ _B ], [T ⁽³⁾ _Max -TX ⁽³⁾ _In ] > [T ⁽¹⁾ _Max -T ⁽¹⁾ _In ], and T ⁽³⁾ _Max > T ^{( 1)} _Max ). Of course, T ⁽³⁾ _Max may be less than or equal to T ⁽¹⁾ _Max when necessary. However, the residence time t ⁽³⁾ _B can be shorter than in known devices. This is due to the fact that, in the device according to the invention, the steam is injected directly into the product line through the steam supply. The temperature of the steam is 150-230° C. and the corresponding pressure is 5-28 bar. Thus, the product can be heated very rapidly with the inventive device of Figure 3 to achieve a shorter residence time and a more limited diffusion during the residence time. Due to the fact that the time of the product at the maximum temperature T ⁽³⁾ _Max is very short, this temperature T ⁽³⁾ _Max can be chosen higher than T ⁽¹⁾ _Max without the product suffering adverse consequences such as protein denaturation . But on the other hand, the brief high temperature T ⁽³⁾ _Max does have the consequence that microbial inactivation is much higher than the 10% reduction rate. In addition, much more thermotolerant spores could be inactivated than a 10% reduction. A high product quality can thus be achieved.

The device is further optimized by providing a flow restriction 30 . This flow restriction 30 is located at the same position as the outflow opening 16 of the product line, so that there is no side wall of the product line downstream of the restriction. The product duct tapers downstream over a length V as far as a restriction 30 . However, this is not necessary, and steeper transitions can also be used. Since the product line does not run downstream of the restriction, the product leaving the restriction will be cooled directly in the expansion vessel. In effect, the restriction is the end of the product line and terminates directly in the expansion vessel. This also means that the cooled product does not clump in the product line downstream of the restriction. Here, see FIG. 3 a , the restriction is also formed with a nozzle located at the terminal end of the product duct in the expansion vessel 10 . By arranging the flow restriction at the end of the product line in the expansion vessel, it is achieved that the product, after reaching the maximum temperature T ⁽³⁾ _Max , ends up very quickly through the flow restriction in the expansion vessel which directly cools the product . The consequence of this is that the product expands in the expansion vessel 10 after a short heating time T ⁽³⁾ _B and a very short cooling time t ⁽³⁾ _D . This cooling time is much shorter than the cooling time t ⁽¹⁾ _C + ⁽¹⁾ _D of the arrangement according to FIG. 1 .

The pressure in the expansion vessel is, for example, 0.02-0.9 bar. The product can be collected through the discharge 18 after it has cooled to 20-90°C. The steam leaves the expansion vessel through opening 20 .

According to the arrangement of FIG. 3 a , the outflow opening is located in the expansion vessel 10 at a position that is offset from the inner wall of the expansion vessel 10 . The product line 8 runs in an opening 34 of the container and is connected in this opening 34 to the expansion container 10 by a thermally insulating seal 36 , for example a Teflon ring. Consequently, the product conduit can remain moderately hot in the vicinity of the combined restriction and outflow, while the walls of the expansion vessel are barely heated. Thus, a possible cake of product on the outside of the product line in the expansion vessel (which is now sealed by the seal 36 ) and on the wall of the expansion vessel is prevented.

In this embodiment, the volume of the product conduit 8 between the steam supply port 24 and the restriction 30 is adjustable. Here, for example, the length L of the product line 8 between the steam supply port 24 and the restriction 30 is adjustable. By increasing or decreasing the length L (the part between B and C; see Figure 3), it is possible to increase and decrease the heat holding time of the product (the time during which the product has a maximum temperature T ⁽³⁾ _Max ) accordingly.

The parameters of the device are set such that in use the steam condenses completely upstream of the restriction. At this point the product temperature is constant and has reached its maximum. This steam then condenses. For example, the parameter setting may include adjusting the product rate, steam flow rate, diameter and/or size of the restriction and/or the diameter of the product conduit.

The device is for example also provided with a sensor 38 for sensing the temperature in a part of the product duct downstream of the steam supply opening 24 and in at least one product supply opening 40 . Via an electrical line 42 the sensor is connected to the steam supply 28 . The steam supply device is configured, for example, to adjust the amount of steam supplied to the product line according to the sensed temperature. In this way, the corresponding maximum temperature T ⁽³⁾ _Max can be accurately sensed and adjusted. Thus, for example, the maximum temperature can be adjusted to a predetermined value.

Preferably, the restriction member has a diameter d of 0.5-5 mm. Specifically, the restriction has a length k which is approximately equal to the diameter of the restriction. It appears to be very advantageous when the restriction is less than 3 mm in length, for example approximately 2 mm in length. In this defined length, no vapor appears to flow out of the restriction, so that the formation of gas bubbles that limit the flow rate due to the achieved maximum critical velocity can be prevented.

In this embodiment, the diameter of the product conduit is approximately 10 mm. In this embodiment, the portion (from A to B; see FIG. 3 a ) in which the steam supply port is provided extends for a length of about 120 mm. For example, each of these steam supply ports has a diameter of approximately 1 mm. For example, the product line is provided with approximately 30 steam supply ports 24 . For example, the expansion vessel has a maximum diameter D of at least 500 mm and a height H of at least 500 mm. In particular, the expansion vessel has a capacity of approximately 180 liters.

When used with a liquid product 4, the restriction also enables the formation of droplets of the product through it in the expansion vessel. Restriction 30 /outflow opening 16 thus simultaneously forms a nozzle. As a result of the formation of droplets, the surface of the product leaving the confinement expands, so that the product will cool more rapidly in the expansion vessel.

With the arrangement in Figure 3a, for example a product flow rate of 100-50,000 l/h can be obtained, which requires eg a steam flow rate of 10-2,000,000 l/h and a condensate flow rate of 10-20,000 l/h.

In a second embodiment according to the invention as shown in FIG. 3 b (corresponding parts in FIGS. 3 a and 3 b have the same reference numerals), the outflow opening 16 is located on the surface of the inner wall 32 of the expansion vessel 10 . This reduces condensation of product on the walls of the product conduit and on the walls of the expansion vessel.

It is to be noted that the present invention is by no means limited to the above-described embodiments. In addition to the liquid product, the fluid product may also include a suspension/dispersion of particles having a maximum dimension of about 10% of the diameter of the restriction.

In order to increase the throughput of the unit, multiple product lines can be connected in parallel, each product line terminating in an expansion vessel. Also, the capacity of each product pipeline can be increased. In this embodiment, each of the steam supply ports is located downstream of at least one product supply port 40 . However, it is also possible, for example, to supply steam and product to the product line via a T-piece.

It should be understood that all these modifications will fall within the scope of the present invention.

Claims (20)

1. Apparatus for treating a fluid product by heat, the apparatus being provided with at least one product line for conveying product and steam in use to treat the product with heat from the steam; and cooling the product line from the product line An expansion vessel for a product, the product conduit being provided with an outflow terminating in the expansion vessel, at least one steam inflow inlet, at least one product inflow inlet and a flow restriction located downstream of the steam inflow inlet and the product inflow inlet to form a flow resistance, so Said flow restriction also forms the outflow of the product conduit, so that there is no side wall of any product conduit downstream of the restriction, and the restriction terminates directly in the expansion vessel, said product conduit extending in an opening of the vessel, It is characterized in that the product line is connected to the container in this opening by means of a thermally insulating seal, and that the outflow opening is located on the surface of the inner wall of the expansion container. 2. The apparatus of claim 1, wherein said at least one steam inflow port is located downstream of said at least one product inflow port. 3. The device according to claim 2, characterized in that the volume of the product conduit between the at least one steam inflow opening and the restriction is designed to be adjustable. 4. The device according to claim 3, characterized in that the length of the product line between the steam inflow opening and the restriction is designed to be adjustable. 5. The device according to any one of the preceding claims, characterized in that the device is dimensioned by adjusting the length L of the product duct between the most downstream steam inlet and the flow restriction so that at In use the steam condenses completely upstream of the restriction. 6. The device of claim 1, wherein the side wall of the product conduit is provided with at least one steam inlet. 7. The device according to claim 1, characterized in that said device is further provided with steam supply means for supplying pressurized steam to at least one steam inflow port. 8. Apparatus according to claim 7, characterized in that the apparatus is further provided with a sensor for sensing the temperature in a portion of the product conduit downstream of the at least one steam supply port and the at least one product supply port. 9. The apparatus of claim 8, wherein the steam supply means is arranged to adjust the amount of steam supplied to the product line in accordance with the sensed temperature. 10. The device of claim 1, wherein the restriction has a diameter of 0.5-5 mm. 11. The device of claim 1, wherein the length of the restriction is equal to the diameter of the restriction. 12. The device of claim 1, wherein the length of the restriction is less than 3 mm. 13. The apparatus of claim 1, wherein the product conduit is provided with a plurality of steam supply ports provided in a side wall of the product conduit. 14. The device according to claim 13, wherein the product pipe has a diameter of 10 mm, the portion in which the steam supply ports are provided has a length of 120 mm, and each steam supply port has a diameter of 1 mm. 15. The device according to claim 14, characterized in that the product pipeline is provided with 30 steam inlets. 16. The device of claim 1, wherein the expansion vessel has a diameter of at least 500mm and a height of at least 500mm. 17. The device of claim 1, wherein the expansion vessel has a capacity of 180 liters. 18. The device of claim 1, wherein, when used with a liquid product, product droplets are formed in the expansion vessel by the restriction. 19. A method of treating a fluid product with heat, wherein the product is conveyed through at least one product conduit with steam to treat the product with heat from the steam, and the steamed product is subsequently Feed to an expansion vessel to cool the product and contain in the product line a restriction by which droplets are formed from the product in the expansion vessel downstream of said restriction in the expansion vessel , characterized in that the method is carried out by means of an apparatus for treating a fluid product using heat, the apparatus being provided with at least one product conduit in use for conveying the product and steam to treat the product using heat from the steam and an expansion vessel for cooling product from a product pipeline provided with an outflow terminating in the expansion vessel, at least one steam inflow, at least one product inflow, and downstream of the steam inflow and the product inflow A flow restriction forming a flow resistance which also forms the outflow of the product pipe, so that there is no side wall of any product pipe downstream of the restriction and which terminates directly in the expansion vessel, the product The conduit extends in an opening of the container in which the product conduit is connected to the container via a thermally insulating seal, and the outflow opening is located on the surface of the inner wall of the expansion container. 20. The method of claim 19, wherein the steam condenses before being delivered to the restriction with the product.

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